stage2: pass some pointer tests

 * New AIR instructions: ptr_add, ptr_sub, ptr_elem_val, ptr_ptr_elem_val
   - See the doc comments for details.
 * Sema: implement runtime pointer arithmetic.
 * Sema: implement elem_val for many-pointers.
 * Sema: support coercion from `*[N:s]T` to `[*]T`.
 * Type: isIndexable handles many-pointers.

1 files changed, 9 insertions, 5 deletions

diff --git a/src/type.zig b/src/type.zig
index 02b9fabe71..28b87a8afe 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -2753,11 +2753,15 @@ pub const Type = extern union {
         };
     }
 
-    pub fn isIndexable(self: Type) bool {
-        const zig_tag = self.zigTypeTag();
-        // TODO tuples are indexable
-        return zig_tag == .Array or zig_tag == .Vector or self.isSlice() or
-            (self.isSinglePointer() and self.elemType().zigTypeTag() == .Array);
+    pub fn isIndexable(ty: Type) bool {
+        return switch (ty.zigTypeTag()) {
+            .Array, .Vector => true,
+            .Pointer => switch (ty.ptrSize()) {
+                .Slice, .Many, .C => true,
+                .One => ty.elemType().zigTypeTag() == .Array,
+            },
+            else => false, // TODO tuples are indexable
+        };
     }
 
     /// Returns null if the type has no namespace.